The invention relates to flexible, sheet-like substrates having an abrasive surface and their use as wiping cloths for cleaning surfaces in the household and in industry.
WO 01/94436 discloses a process for the production of resilient foams based on a melamine/formaldehyde condensate. In this process, an aqueous solution or dispersion which comprises a melamine/formaldehyde precondensate, an emulsifier, a blowing agent, a curing agent and, if appropriate, customary additives is foamed by heating to 120 to 300° C. and the precondensate is crosslinked. The molar ratio of melamine to formaldehyde is greater than 1:2. It is, for example, from 1:1.0 to 1:1.9. The open-cell, flexible foams thus obtainable are used mainly for heat and sound insulation of buildings and parts of buildings, for heat and sound insulation of the interiors of vehicles and aircraft and for low-temperature insulation, for example in cold stores. The foams are also used as insulating and shock-absorbing packaging material and, owing to the great hardness of crosslinked melamine resins, for mildly abrasive cleaning, abrasive and polishing sponges.
U.S. Pat. No. 6,713,156 describes sheet-like substrates whose surface displays an abrasive effect when rubbed on other articles. Such abrasive substrates are obtained, for example, by spraying, foaming or printing polymers onto a sheet-like underlay, such as nonwovens or paper, by applying the polymers nonuniformly thereon and curing them. The curing of the polymers must take place rapidly because a nonuniform application of the polymer is responsible for the abrasive effect of the substrate. The polymer compositions used have a minimum film formation temperature (MFT) of more than −10° C. and comprise at least one polymer having a Tg of at least 0° C., in general from 20 to 105° C. The polymer composition may comprise up to 20% by weight of additives, e.g. plasticizers, crosslinking agents, starch, polyvinyl alcohol, compositions heat-curable with formaldehyde, such as melamine, urea and phenol. The amount applied is in general more than 20% by weight, preferably from 30 to 50% by weight, based on non-wovens and other porous substrates. The substrates coated nonuniformly with polymers are used, for example, as scouring cloths and as wiping cloths in the household and industry, as cosmetic wipes and as swabs for wound treatment.
US 2005/0202232 discloses products which consist of at least one sheet-like melamine foam layer and at least one reinforcing layer. Basotect® from BASF Aktiengesellschaft is mentioned as the melamine foam. Basotect® is an open-cell foam based on a melamine/formaldehyde condensate. The sheet-like melamine foam layer and the likewise sheet-like reinforcing layer comprising cellulose fibers or natural or synthetic textile fibers are bonded to one another, for example, with the aid of a hotmelt adhesive. However, depending on the type of reinforcing layer, they can also be combined directly with one another, for example by the action of heat and, if appropriate, pressure. The products thus obtainable, which have a melamine foam layer on at least one side of the sheet, are used as articles for the cleaning and care of surfaces in the household and in industry, owing to the great hardness of the melamine foam layer. These are preferably disposable articles which are disposed of after use. In general, they are cloths which have a thickness of less than 5 mm, preferably from 0.85 to 2 mm.
Glues and impregnating resins which in each case are sold as aqueous binders or powders based on condensates of urea, melamine and formaldehyde, as Kauramin® and Kaurit® from BASF Aktiengesellschaft, 67056 Ludwigshafen, are used in the furniture and construction industry for the production of board-like board-base materials, such as particle boards, plywood boards and formwork boards, cf. Technische Information Kaurit®. Papers impregnated with impregnating resins have a hard surface. Such products are present, for example, in surfaces of laminate floors or in the decoration of articles of furniture, cf. Technische Information Kauramin®.
In order to increase the wet strength of paper, for example, melamine/formaldehyde resins are added to the paper stock prior to sheet formation in the production of paper, e.g. Urecoll® K, BASF Aktiengesellschaft, 67056 Ludwigshafen. The amounts of resin present in the paper stock are, for example, about 0.5 to 1% by weight, based on dry paper stock.
Known wiping cloths, such as kitchen roll or tissue, which are intended to be disposed of after use, do not have sufficient stability, particularly in the moist state, to ensure an adequate wiping effect.
The prior EP application 06 116 165 discloses a process for the finishing of paper and paper products with at least one finishing composition, at least one finishing composition being applied in the form of a pattern to the top and/or bottom of paper or paper products. In this process, smaller amounts of finishing compositions are required in comparison with known finishing processes in order to produce papers having comparable properties. Suitable finishing compositions are, inter alia, also melamine/formaldehyde resins and urea/formaldehyde resins.